Planarity and the horizontal alignment of the measurement site play a major role in wheel alignment. Furthermore, there is interest in determining the rolling radius, i.e., the distance between the wheel contact surface and the rotation center of the wheel, for the handling of errors and defects, for example, chassis defects or uneven air pressure in the tires.
Optical measurement systems based on marks, such as those in U.S. Pat. No. 6,237,234 B1, for example, are believed to be understood for this in the related art. With these systems, the center of the wheel is determined with the aid of marks (“targets”) mounted on the wheel.
The position of the road surface may also be determined online or offline by mounting additional marks at a known distance from the surface of the measurement site (road surface) (see, for example, U.S. Pat. No. 7,869,018 B2).
For determining the rolling radius using such methods, marks on the wheel are also necessary in addition to marks provided on the surface of the measurement site or the vehicle platform. It is time-consuming to mount the marks and under some circumstances this may even cause damage to the wheel rims.